7. Carbon Sequestration

The earth has been losing soil organic carbon to the atmosphere since historic times, a process greatly accelerated within the past 50 years; as agriculture intensifies, and forests are cut down to convert to agricultural land. Estimates for the historic losses of soil organic carbon range widely from 44 to 537 Gt, with the common range of 55 to 78 Gt. That is the amount we can theoretically put back from the atmosphere into the soil as organic carbon, if we get our agriculture and land use right.
There is significant potential for sequestering, or taking carbon from the air into the soil through a set of recommended management practices. On existing croplands (1.35 billion ha), maximize soil organic carbon and fertility through organic inputs, cover crops, conservation tillage and mixed farming; on rangelands and grasslands (3.7billion ha), prevent overgrazing, fires and loss of nutrients, on degraded and desertified land (1.1 billion ha), prevent water and wind erosion, harvest and conserve water and plant forests; and on irrigated land (0.275 billion ha), control salinity, use drip/sub-irrigation, provide drainage, enhance water efficiency and conservation. [1]

The USDA National Agro-forestry Centre [2000] agrees that carbon sequestration under agro-forestry is particularly high. The Agro-forestry Centre suggests that, with coppicing, soil carbon can be increased by 6.6 tonnes C/ha/yr over a 15-year rotation and wood by 12.22 tonnes C/ha/y over the rotation. [2]
 
Agro-forestry and carbon sequestration go hand in hand. If we see carbon constant in the world and only changing its form as solid, liquid or gas one of the methods is to capture carbon from atmosphere to soil because carbon in gas form increases temperature of the atmosphere. Carbon in the solid form is found largely in the forest land so one of the ways to mitigate global warming is carbon sequestration.

Agro-forestry (combining trees and crops together or in sequence) is now being increasingly recognized globally as having substantial potential to serve as a carbon sink to reduce the load of harmful gases in the environment.

Significantly, the new collaborative agro-forestry project aims especially at developing environment-friendly technologies which small and resource-poor farmers can adopt. It will evolve novel agro-forestry systems which may require the introduction of new tree species, besides promotion of the known ones, having good potential for sucking in carbon dioxide. These systems, moreover, will have the capability to adapt to emerging conditions and mitigate the climate change process. The new plant species will, of course, be introduced after due diligence about their complementarity with agro-ecology and prevailing cultivation practices. This will be ensured by undertaking the complete life cycle analysis of the new agro-forestry systems before introducing them. [3]